If pension sharing is going to feature in your divorce, you will probably need a report from a pensions expert.  People are understandably put off by the cost of a report, which will normally be at least £500, but it is a false economy to try to manage without.  

Only a pension expert (an actuary or an independent financial adviser with the pension 'ticket') has the ability to advise on the percentage pension share needed to achieve a particular outcome, such as equality of income in retirement.  It is not safe to assume that a 50% pension share (i.e. the spouse with the pension gives the spouse without a pension 50% of the transfer value of the pension) will achieve equality of income.  It almost certainly won't.